In recent years, there has been a development in technology that has been applied in the automation of houses, buildings, etc., which has been termed as home automation or domotics.
A key part of home automation is the automation of lighting systems, with devices such as intelligent switches, also known as smart switches. With the quick development of these technologies, people have begun to adopt smart switches for their homes. Smart switches allow a user to turn on and off, dim a lighting device, control it remotely or measure power consumption.
Smart switches usually need three wires to function, that is, a hot wire from the alternating-current (AC) source is connected to one terminal of the smart switch, a second wire is connected to another terminal of the smart switch and the lighting device, and a neutral wire from the AC source is connected to a third terminal of the smart switch, which closes the circuit inside the smart switch, allowing current flow for the operation of the electronics of the smart switch.
Usually, the electrical wiring of homes has only the first two wires in a switch box or wallbox, with the neutral wire absent from the switch box, since common (non-smart) switches or dimmers are connected in series between the AC source and the lighting device. This yields the problem of having to rewire the entire home in order to bring a neutral wire from the AC source to the switch box.
Some smart switches measure the power consumption by means of their power supply. Said power consumption is calculated for an entire circuit (one way, line, or gang), i.e. for all the electric loads combined connected to the circuit. Therefore, a user cannot measure the power consumption of each individual load. The power consumed by each individual load is useful to know if a lighting device is consuming more power than usual or to know when to replace a lighting device.
A power source for a two-wire smart switch is disclosed in U.S. patent application Ser. Nos. 12/952,920 and 15/131,444 and their families. However, said implementations need an adapter or artificial load for each circuit to be controlled by the switch, i.e. one adapter for each switch in a gang switch. Another two-wire power supply for a smart switch is described in U.S. Pat. No. 8,892,913 B2. However, the power delivered by said power supply is very low, since it is provided by a capacitor that gets charged near the zero-crossing of the AC wave. If the capacitor is not fully charged, the power supply may turn off some of its elements, like an LED or a communications module. Another disadvantage of US '913 B2 is that the circuit is fairly complex, requiring a microprocessor to control the power supply. The microprocessor is powered by the power supply, therefore, if any of the two were to fail, the other would fail too.
A device for power measurement is disclosed in U.S. patent application Ser. No. 14/991,133, however, said device does not measure the power consumption of an individual load, but the combined loads in a circuit.
The power measurement in a two-wire load control device described in U.S. Pat. No. 9,250,669 B2 discloses a current measuring circuit that includes only a resistor (e.g., a micro-Ohm resistor) that may be used to measure a current to be inputted in ADC, that passes through the two-wire load control device. Wherein the control circuit is electrically connected between the controller and a controllably conductive device (a bidirectional semiconductor). However, the two-wire load control device can only operate one conductive device, therefore, control only a single lighting load at the same time. Additionally, the two-wire load control device relies on an energy storage device (a capacitor), therefore the power is not supplied continuously.
Another dimmer switch for use with lighting circuits having three-way switches is described in U.S. Pat. No. 7,687,940 B2. However, the smart switch can be installed only in three or four-way switches systems, wherein the lighting control system has implemented a sensing circuit that has a current sense transformer that only operates above a minimum operating frequency, for example, 100 kHz, such that current only flows in the secondary winding when the current waveform through the primary winding has a frequency above the minimum operating frequency, wherein the system includes only two controllably conductive devices or bidirectional semiconductor switches, such as a TRIACs. However, the power supply of the system sometimes is unable to supply power to the controller through the duration of a toggle or switching of the three-way switch, and the controller of the system will reset.
A load control device for high-efficiency loads is disclosed in U.S. Pat. No. 9,343,997 B2, U.S. Pat. No. 9,343,998 and U.S. Pat. No. 9,853,561 B2. The control device comprises only one bidirectional semiconductor switch that comprises a control input (e.g., a gate), which may receive control signals for rendering the bidirectional semiconductor switch conductive and non-conductive. However, the load control device has a mechanical switch that controls the powering of the whole device, and when the mechanical switch is off, the system is unpowered, therefore requiring the physical input from a user to reactivate the load control device. Additionally, the load control device it is limited to control only one lighting load at a time.
A smart electronic switch for low-power loads is disclosed in U.S. Pat. No. 8,922,133 B2 and U.S. Pat. No. 9,418,809 B2, wherein the electronic switch comprises two power supplies: an on-state power supply and an off-state power supply. Both power supplies, operate to generate a DC supply voltage across an output capacitor. Wherein the electronic switch has implemented a bidirectional semiconductor switch that is coupled in series electrical connection with the parallel combination of a relay and an on-state power supply. The on-state power supply operates to generate the DC supply voltage when the relay is closed and the lighting load is on. However, this system is not compatible with a three-wire switch box. Additionally, the two-wire load control device relies on an energy storage device (a capacitor), and a relay, which are prone to failure.
Therefore, is desirable a power supply for a smart switch that operates with two or three wires and controls up to three lines with multiple lighting devices, with only one adapter per line, supplies enough power to power a microcontroller or microprocessor, a user interface and a communications module; and measures power consumption of individual lighting loads.